I74
WILLIAM MACNAE
The " avicennia parklands " may have a soil surface of coarse,
medium or fine sand, and bare areas occur between the clumps and
clones of Xesuvium portulacastrum and species of Arthrocnemum. Where
the sand is coarse t o medium, U . lactea is abundant. On Australian
shores, when the sand is fine to very fine, U . bellator (White) occurs.
The sandy floors of drainage channels between the trees are often
colonized by Macrophthalmus depressus (Ruppell) and at low tide these
crabs may be found buried in the moist sand. They seem t o migrate
upward during spring tides and downwards at neaps.
There is no equivalent of these in the ever-wet of South East Asia
where U . lactea (in both forms) seem to be limited in distribution to
slightly sandy areas in clearings, or to more open beaches of sandy mud.
I n eastern Africa from the Bay of Lourengo Marques northwards
wherever bare areas have developed between the mangroves and high
water mark, portions or the whole of these will be colonized by Uca
inversa (Hoffmann). These crabs are most abundant in areas of fine
to medium sand. They come to the surface t o forage and display only
on the few days of spring tides, just after the tide has ebbed. At neap
tide periods the burrows are blocked from within.
I n Australia such areas are colonized by Uca bellator but this species
does not penetrate so far towards the centre of the bare, sun-baked,
salty flats.
I n the ever-wet of South East Asia and north central Queensland,
where the landward fringe consists either of rain forest or scrub forest,
the crabs and crustaceans from lower levels will come higher up. There
is less necessity for specializations to withstand desiccation. Snails
will be abundant in the litter. These are representatives of families
which have freshwater and brackish water species.
The prosobranch families Synceridae (= Assimineidae) and Neritidae and the pulmonate families Ellobiidae and Amphibolidae provide
several species associated with this landward fringe and some of them
penetrate downwards into the bruguiera forest. The following are
characteristic in Malaya and adjoining areas :
Cassidula mustellina (Derh.)
cLurisf elis (Brug . )
Ellobiur~ auris-judae (L.) (Fig. 55C)
aztris-midae (L.) (Fig. 55A)
Nerita birmanica Phil.
Pythia scarabaeus (L.) (Fig. 55E)
Cerithidea obtusa (Lam.)
alata (Phil.)
2 . The bruguiera forests and ceriops thickets
Both the bruguiera forests and their variant, the thickets of Ceriops
tagal, are densely shaded and normally the soil is quite firm. There is
only a slight tendency for litter to accumulate, but fallen branches and
WILLIAM MACNAE
The " avicennia parklands " may have a soil surface of coarse,
medium or fine sand, and bare areas occur between the clumps and
clones of Xesuvium portulacastrum and species of Arthrocnemum. Where
the sand is coarse t o medium, U . lactea is abundant. On Australian
shores, when the sand is fine to very fine, U . bellator (White) occurs.
The sandy floors of drainage channels between the trees are often
colonized by Macrophthalmus depressus (Ruppell) and at low tide these
crabs may be found buried in the moist sand. They seem t o migrate
upward during spring tides and downwards at neaps.
There is no equivalent of these in the ever-wet of South East Asia
where U . lactea (in both forms) seem to be limited in distribution to
slightly sandy areas in clearings, or to more open beaches of sandy mud.
I n eastern Africa from the Bay of Lourengo Marques northwards
wherever bare areas have developed between the mangroves and high
water mark, portions or the whole of these will be colonized by Uca
inversa (Hoffmann). These crabs are most abundant in areas of fine
to medium sand. They come to the surface t o forage and display only
on the few days of spring tides, just after the tide has ebbed. At neap
tide periods the burrows are blocked from within.
I n Australia such areas are colonized by Uca bellator but this species
does not penetrate so far towards the centre of the bare, sun-baked,
salty flats.
I n the ever-wet of South East Asia and north central Queensland,
where the landward fringe consists either of rain forest or scrub forest,
the crabs and crustaceans from lower levels will come higher up. There
is less necessity for specializations to withstand desiccation. Snails
will be abundant in the litter. These are representatives of families
which have freshwater and brackish water species.
The prosobranch families Synceridae (= Assimineidae) and Neritidae and the pulmonate families Ellobiidae and Amphibolidae provide
several species associated with this landward fringe and some of them
penetrate downwards into the bruguiera forest. The following are
characteristic in Malaya and adjoining areas :
Cassidula mustellina (Derh.)
cLurisf elis (Brug . )
Ellobiur~ auris-judae (L.) (Fig. 55C)
aztris-midae (L.) (Fig. 55A)
Nerita birmanica Phil.
Pythia scarabaeus (L.) (Fig. 55E)
Cerithidea obtusa (Lam.)
alata (Phil.)
2 . The bruguiera forests and ceriops thickets
Both the bruguiera forests and their variant, the thickets of Ceriops
tagal, are densely shaded and normally the soil is quite firm. There is
only a slight tendency for litter to accumulate, but fallen branches and